For anyone hunting the cheapest flights on the web, key bookmarks are the “meta-search engines”. These sites trawl airlines, online travel agents (OTAs) and flight-data wholesalers to find the best price. But which of them is the cheapest?

I selected 20 routes from Britain to long- and short-haul destinations, plus one internal flight in the United States and one between Australia and Asia. I mixed five different dates, ranging from a short-notice week away in February to a 20-night August trip. I searched for every flight on eight leading flight websites, rejecting prices if they were only available with crazy layovers or a circuitous route. In other words, I chose the cheapest sensible route.

Across my bundle of 20 flights, momondo (momondo.com) was cheapest. Only an insignificant £100 in total separated the top three of momondo, Skyscanner (skyscanner.net) and Kayak (kayak.co.uk). TravelSupermarket (travelsupermarket.com) almost matched the top three on 18 routes, but only offers flights that begin or end at a UK airport.

I took most searches through to the final stage before booking, to verify prices were “live”. In the past, flight engines often “found” prices that no longer existed when the traveller clicked through to pay. This happened only a couple of times in 160 searches.

The best sites usually match each other flight for flight, to within a few pounds. However, Kayak found a London–Hanoi routing that was cheapest by £35; momondo beat all rivals by £40 on a Manchester to Nairobi flight in August. Kayak, Skyscanner, and momondo were among the quickest to return results, though every engine was slower than Google Flight Search (google.co.uk/flights). The Google tool, however, was no match for the specialists when it came to finding the best prices. In fact, Google Flight Search came eighth in price performance, almost 12 per cent more expensive than momondo for my basket of 20 flights.

“Google Flight Search is a new feature and we are still developing our partnerships and coverage. This week's announcement – that Ryanair has joined Google Flight Search – means we now have some of the cheapest airfares across Europe, and we look forward to striking more airline deals across different regions,” said a Google spokesperson.

So, there's no definitive "cheapest" site to book your flights, and which is “best” depends on how you rate their unique features. Kayak's Price Trend graph analyses route price movements over 90 days to advise whether you should book immediately or wait for a fall in price. Google Flight Explorer (google.co.uk/flights/explore) has handy bar charts to help you compare flight prices to vague destinations, like “Italy” or “the Caribbean”. TravelSupermarket has fewest extra features, but is “rebuilding its flights engine from the ground up,” according to the company, for relaunch later in 2014.

Adioso (adioso.com) offers the most radical rethink of flight search. As well as the usual destination- and date-based queries, Adioso's engine accepts vaguer searches, in natural language. Type “London to Southeast Asia mid May for 3 weeks” into the search box and Adioso suggests flights. Although Adioso didn't match established players on price, it performed respectably, with my bundle of 20 flights around 4 per cent more expensive than Kayak. Expect “some big improvements on price data in the coming months,” says Adioso's co-founder, Tom Howard.

Hipmunk (hipmunk.com) has a clear interface which recognises that the cheapest flight is not always the best option. It ranks flights by “Agony,” weighing up cost and the inconvenience of multiple stops and long layovers. Search results on momondo work similarly, ranking flights in cheapest, quickest and “best” tabs.

So, rather than relying on one search to find the cheapest flight, I suggest you get in the habit of cross-checking at least three. If I was booking a flight today, I would probably use Kayak, momondo and Adioso.

This article was originally published on January 11, 2011, and updated in full on January 23, 2014.